| The straw is a kind of versatile renewable biological resources,including more than half of the photosynthesis product which is made by crops,and the straw is rich in nitrogen,phosphorus,potassium,organic matter and so on.However,the straw discarded or burned for a long time in China,which caused serious pollution and restricted the sustainable development of the environment in China.Therefore,utilization of straw resources effective is the urgent problem of environmental sustainable development and agricultural production practice in China.Straw can be used as an important source of roughage for herbivorous livestock,and its nutritional value has certain advantages.In addition,attention should be paid to the ability of herbivorous livestock to digest straw.However,the research on the relationship between the variation of nutrient composition of straw in different nutritional periods and digestibility is still very weak,especially the research on different organ levels is even more rare.Therefore,it is of great significance to strengthen the research on the forage utilization of the main organ nutrients of straw for improving the forage efficiency of straw,and at the same time to provide scientific basis for rational utilization of straw and improving the forage utilization efficiency of straw.In this experiment,Zea mays L.was taken as the research objects.Through the field experiment,maize samples were taken every four days from August 20,2020 to October 20,2020,and a total of 14 times were sampled;two different components:stem,leaf sheath.Each treatment was repeated 12 times.Three different organs of stem,leaf and sheath were sampled from segment 1 to segment 16 of corn straw at three important periods during the sampling period: September 7,September 30 and October 15.The chemical compositions and changes in in vitro digestibility of different organs in different nutrition stages and different segments of maize.Changes in the content of large,medium and trace elements(potassium,calcium,magnesium,sulfur,sodium,boron,chromium,zinc,cobalt,molybdenum,silicon,manganese,iron,copper)in different corn organs at different nutrition periods.And the following main results were obtained:(1)The straw yield of maize decreased with the increase of development time,which indicated that the vegetative growth of the straw was completed in the early development,and the yield decreased due to weathering in the later period.Different organs of the plant contributed differently to the total yield.(2)The nutritional value of maize decreased with the development stage.The crude protein(CP)content of steam and leaf sheath decreased by 36%,55.7%,respectively.This may be because the plant had completed nitrogen absorption during the maturation process,thereby diluting the nitrogen concentration and reducing the CP content.The content of ether extract,soluble sugar and sucrose in corn stalks also decreased with the increase of development time.(3)The fiber content of maize plant increased with the development stage.The neutral detergent fiber(NDF)of the stem and leaf sheath of the corn plant increased by 14%,18% with the development period,the acid detergent fiber(ADF)increased by 7.7%,8.7%,the acid detergent lignin(ADL)increased 3.9%,2.1%,hemicellulose increased by 6.6%,9.3%,cellulose increased by 3.7%,6.6%.This indicated that the degree of lignification of straw increased with the increase of development time,which led to a decline in the digestibility of straw by herbivorous livestock.(4)In the study of the nutritional value of different components(stem,leaf,sheath)in different segments of corn at three stages(September 7,September 30 and October 15),it was found that the NDF,ADF and hemicellulose of steam increased with segment increasing,with an average increase of 11.9%,9.4%,11.9%.The NDF,ADF of leaves and sheaths decreased with the increase of segments,and decreased by11.9%,8%,16.5%,10.2%,respectively.The results showed that the proportion of non-lignified tissues such as mesophyll cells in leaf and sheath increased with the increase of segments,which led to the decrease of fiber content.(5)The highest amount of silicon was found in maize plants,and the lowest was cobalt.The content of Si,Co,B,Na,S,K,Ca,Mn and Cu were the highest in leaves.The content of Mo,Cr were the highest in bracts.The highest content element in cob were Mg,Fe.Zn content was the highest in the grain.The content of Co,B,Mg,Ca,Mn were the highest in the silage stage.The content of Si,Mo,Fe,Cu,Zn and S were the highest when the sample was taken on September 7.The content of Na,K and Cr were the highest on October 20..(6)There were significant differences in in vitro digestibility(IVDMD)at the organ level.IVDMD also varied with the vegetative period,IVDMD of leaf sheath decreased by 20% at different stages.IVDMD of different organs had different changes in different segments,the stem IVDMD decreased by 31%,the leaf and sheath IVDMD increased by 3% with the increase of segments..In conclusion,the straw yield of maize decreases with the increase of development time.The nutritional value of corn straw decreased significantly with the development stage,while the fiber content of corn straw was increased with the development stage.The fiber content of steam of maize increased with the increase of segments,while the fiber content of leaf and sheath decreased with the increase of segments.The results of this study revealed the changes of nutrient value of straw fiber content and in vitro digestibility from a new perspective of organs and different segmental levels,and provided a theoretical basis for the effective utilization of straw. |
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